Fairphone 3 - Forgot PIN - recover with Google "Findy my phone" not possible?

Hi,

I lost my telephone PIN for Fairphone 3 and I want to recover this with the Google “Find my phone” service.

But allthough the smartphone is online with WLAN and mobile network Google could not contact it. It was contacted 1 day before, so it principiell is working. Then it was powered off overnigth.

How can I force that the smartphone could be find again? Or is it not possible after a reboot?